Research to explore the treatment and reuse of water using biochar

Researchers at Colorado State University (CSU) recently received funding to start a research project to create new sustainable uses for non-traditional water sources.

The CSU team received a $ 1.9 million grant from the National Alliance for Water Innovation of the United States Department of Energy, a multi-institutional network of scientists focused on treatment technologies and reuse of original water sources such as municipal wastewater, seawater and agricultural drainage.

Thomas Borch, professor in the Department of Soil and Crop Sciences with joint nominations in Chemistry and Civil Engineering, leads the award-winning CSU research team and is also a member of the national alliance leadership team.

Reduce water demand

Borch and the team will focus over the next two years on the development and testing of inexpensive, environmentally friendly materials that work as chemical absorbents, similar to sponges, for the precise disposal and recovery of certain nutrients – mainly phosphate, ammonium and nitrate – from municipal and agricultural wastewater. Their test bed will be a functioning wastewater treatment facility on the Hawaiian island of Maui, operated by Washington-based water treatment solutions company WaterTectonics. WaterTectonics CEO Jim Mothersbaugh will serve as a key research partner in the project.

The benefits of a successful business would be manifold, according to the researchers. Wastewater treatment and reuse would reduce the demand for freshwater in many sectors, including agriculture. Phosphates and other nutrients recovered from this water could become valuable and environmentally friendly fertilizers for agricultural fields. In addition, their work could lead to an overall reduction in the levels of phosphates and nitrates typically left in wastewater and ending up in lakes and oceans. These nutrients fuel harmful algal blooms, disrupting delicate ecosystems, including fish and aquatic plants.

“The volumes of water we’re talking about are just huge,” Borch said. “Agriculture alone is responsible for over 42 percent of all freshwater withdrawals in the country. If you really want to make a difference when it comes to water treatment and reuse, you will need to focus on the agriculture or power sectors.

Explore biochar

The starting absorbent materials chosen by the researchers will be optimized and chemically adapted biochar and clay, which will be functionalized by the addition of metal oxides and biodegradable polymers. Biochar, commonly referred to as a soil additive, is a charcoal-like material created by burning carbon-rich biomass – typically wood, wheat straw, corn stalks, or manure – in an environment without oxygen. Its potential as a low-cost material for the precise separation of nutrients from water is being explored by several scientists, including the CSU team.

For this project, the team plans to use biosolids waste from the Maui processing plant as a feedstock to make their biochar sorbents. Other members of the University of Cincinnati research team will work on optimizing clay as an absorbent material.

Jim Ippolito, CSU Associate Professor in the Department of Soil and Crop Sciences, will work on the synthesis and optimization of biochar. Expert in transforming raw materials – including biosolids generated by wastewater treatment facilities – into valuable, nutrient-rich products for application to agricultural land, Ippolito will provide key expertise both in the manufacture of biochar and in fine tuning its absorbent properties.

“The main concept of our proposal is to determine a means by which we can selectively remove even larger amounts of phosphorus and nitrogen from this water,” Ippolito said. “It is relatively difficult to remove these two elements simultaneously from the water column. Our goal is to create new materials to perform the removal for us, while also capturing these nutrients so that they can be reused as a source of fertilizer.

The Maui plant has a pyrolysis unit under construction for the conversion of biosolids to biochar. Their intention is to use the manufactured biochar as a nutrient removal sponge for the wastewater. The nutrient-laden biochar will then be used for agricultural applications in Maui, for which there is a high demand. Converting municipal biosolids to biochar will reduce the cost of biosolids management while contributing to the facility’s sustainability goals and reducing its carbon footprint.

The CSU team will work with WaterTectonics and the local plant operator to manufacture the biochar, characterize its chemical structure, and develop a sustainable solution for nutrient recovery from plant waste.

“We are directly exploiting the work in progress, but we will be responsible for the development of advanced absorbent materials for selective nutrient removal with WaterTectonics,” said Borch.

Scalability and economic viability are a key goal of the project, which is why researchers are choosing simpler materials like clay and biochar, rather than rare and more exotic materials. “Exotic materials might work better as absorbents, but they would be prohibitively expensive and only serve an academic exercise,” Borch said.

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